LANs, WANs, Enterprise Networks and Network Equipment

1. The Management of Telecommunications Houston H. Carr and Charles A. Snyder LANs, WANs, Enterprise Networks and Network Equipment Chapter 8

2. Introduction • Networks at the internal layer, whether analog or digital, connect the organization and give it a cohesive quality

3. Model of network connectivity

4. Metropolitan Area Network (MAN) • MANs cover a metropolitan-sized area such as a city. • MANs give a city a competitive advantage. • Technically oriented organizations looking to locate new operations consider the availability of Internet access as one of the criteria. • A major form of MAN is the fibber distributed data interface (FDDI).

5. Wide Area Network (WAN) • WANs cover a wide geographical area. • WANs go beyond the boundaries of cities and can extend globally. • WANs connect widely dispersed machines, possibly requiring intermediary machines to make conversion from one standard to another. • The extreme of a WAN is a Global network.

6. Value Added Network (VAN) • A Value Added Network (VAN) is a special form of WAN. • VANs generally provide wide area coverage and offer services in addition to connectivity in the form of added intelligence such as; • Speed translation • Store-and-forward messaging • Protocol conversion • Data handling • Packet assembly and disassembly • VANs are nonregulated

7. Packet Data Network (PDN) • The most used PDN uses a virtual channel (VC) • The VC is a predetermined path through the cloud, composed of a number of shared links. • If a link is disabled, the VC will be reestablished over a working path.

8. Packet Data Network

9. Packet Data Network (PDN) • PDNs provide connectivity to many points geographically. • PDNs appear as a cloud with many entry/exit points in many locations. • The internal working of the network are obscured from users because of the way connectivity is provided. • Connections are made using virtual circuits.

10. Packet Data Network (PDN) • A second form of PDN uses datagrams for data transfer. Data is packetized and sent over the network, much like a letter appears to do in postal service. • The packet contains sufficient data to find its way from source to destination. • Datagrams, though not often used, are an efficient use of the PDN.

11. Attachment to a PDN • Each attach point has a Packet Assembler/Disassembler (PAD) • The PAD takes the total data block and • Breaks it into predetermined-sized packets • Adds the appropriate addressing, administrative, and error checking data to the packet, then • Places the packet on the network.

12. VANs and PDNs • VANs in general, and PDNs in particular, offer services that • are reliable, • are national and international in coverage, • have low error rates, • offer a variety of speeds, and • are cost effective.

13. Local Area Network (LAN) • A LAN is a group of machines connected in a relatively small area, where the uses are somewhat homogeneous. • LANs have essential parts , such as network adapter cards, cables, hubs, servers, and operating systems.

14. Local Area Network (LAN) • A LAN provides connectivity over a limited area, often less than one kilometer in radius and connecting people within an organization, such as a campus, building, department, floor, or work group. • LANs are normally privately owned and are non-regulated. • LANs can be of any topology.

15. Network Adapter Card • A network adapter card provides an interface between the computer and the network operating system (NOS).

16. Network Operating System (NOS) • The Network Operating System is to the network as Operating system (OS) is to the computer. • The NOS contains the protocol; determining access and handling collisions. • The NOS in some protocols resides on the server. • The Microsoft Windows operating system contains an NOS.

17. Electronic Mail • Electronic mail is the driving force for the installation of LANs. • Organizations are installing LANs to allow this communication, with resource sharing being of lesser consideration.

18. Backbone network • A backbone network gives structure to dispersed networks and nodes • Provides higher speed connectivity between LANs and major nodes, such as mainframe computers, Internet access points and teleports.

19. Geographic or Layer Network Concept

20. Wide Area Networks • Wide area networks (WAN) connect widely dispersed machines, possibly requiring intermediary machines to make conversion from one standard to another.

21. Virtual Private Network (VPN) • A VPN uses a public network, such as the Internet, but includes software that is intended to make the users of the network very secure. • A VPN acts as a virtual tunnel inside the larger network. • VPNs use encryption techniques called “tunneling”, ensuring that the data traveling over the public can not be read by it.

22. Peer-to-peer (P2P) computing • Peer-to-peer (P2P) computing has two forms. In the Napster model: • Each computer in the network gets information from every other computer rather than getting it from one large, central computer. • Collective resources of the entire network are at the command of each connected computer. • Data reside on individual computers rather than on central servers. • In the SETI and United Devices model: • The central node sends tasks to individual nodes. • Processed results are returned to the central node.

23. Grid computing • P2P computing is also called grid computing when a central mainframe or server sends tasks to connected nodes to work in parallel instead of processing them itself in series. • P2P and Grid computing take advantage of otherwise idle processing resources.

24. Internet • The Internet is a Global WAN. • It is a network comprised of networks. • The Internet is a TCP/IP protocol packet data network providing connectivity from almost anywhere to almost anywhere, at a moderate communication speed.

25. LAN Protocols • IEEE protocols for the three most popular LANs • IEEE 802.3 is the standard for CSMA/CD • IEEE 802.4 defines the token-passing bus • IEEE 803.5 defines the token-passing ring • IEEE 802.6 defines the protocol for the Metropolitan Area Network (MAN)

26. Considerations for choosing a LAN

27. Ease of connectivity Vendor support Expandability Performance Ease of use Cost Flexibility Vendor profile Reliability Expense Security Portability Speed Some considerations in LAN selection and LAN operating system

28. WAN Protocols • X.25 • A publicly based network switching system • Makes a temporary physical connection (virtual connection) between two locations • Allows the conversation to occur • Completion breaks the physical connection to the middle carrier trunks can be used by someone else. • Traffic direction is dynamic.

29. Packet Switching

30. X.25 Packet-Switched Network (two node)

31. X.25 Layers and Frame Structures

32. OSI and X.25 • Physical layer – incorporates specifications such as • What type of wire medium (UTP, TP, STP, coax, etc.) • What type of connections (RJ, V.35, RS-232, etc.) and end link transport speeds (2.4-56 Kbps). • What the electrical voltages on the pins will be (spread +/- 5 to 25 volts DC). • What the signal will be (master, slave, clocking and synchronization, etc.)

33. OSI and X.25 • Data Link Layer – describes specific data link protocol efforts such as • Delimiting pointers for start and end of X.25 formatted packets. • Packet numbering and accountability. • Packet acknowledgement, error control, and flow control. • SDLC or HDLC parameters.

34. OSI and X.25 • Packet level (network layer) - controls • Virtual network establishment between network switches • Network interface and DNIC (Data Network Identification Connection) addressing. • Routing. • Carrier interconnection flow control.

35. Network Devices

36. Repeaters • A repeater is the simplest type of hardware that can be used to connect network segments. • Receives a signal and regenerates it. • Operates at the physical layer of OSI model. • Transparent to data flow. • Repeaters are used mainly to extend coverage of a network by extending the length of any segment.

37. Bridges • A bridge is a device that reads data frame addresses, then uses the information to perform transmitting or translation functions. • Uses a combination of hardware and software to connect LANs that have the same or different data link layers, but the upper protocols must be the same. • Operates at the data link layer of OSI model. • More powerful than repeaters, but slower and more expensive to use.

38. Bridges • There are two general types of bridges. • Transparent • Connect two LANs with the same data link protocol. • Translating • Connect two LANs that use different data link protocols. • A bridge is a special purpose computer

39. Transparent Bridges • A transparent bridge examines each frame that is processed a the data link layer • Reads source address of each frame and compares the address to a table of local addresses it maintains for each network. • If the address is not in the table, the bridge will insert it (a process called learning). • Also examines destination address of each frame and compares it to the table it has built • If address matches an entry in the local address table, it repeats the frame. • If address does not match, then the bridge transmits the frame to the other network (a process called forwarding). • If addresses are compared and the bridge determines that a station has already received a message, then the frame is discarded (a process called filtering).

40. Transparent bridge • Techniques used by transparent bridges • Spanning tree protocol (STP) • Algorithm mainly used in Ethernet environments • Disables links and converts the loop into a tree topology • Creates a unique path for each node. • Source routing • Developed by IBM for token ring networks. • Part of information field in frame carries routing information • Discovery packets act as trail guides • The bridge floods the packet to all of the bridge’s connections, but not to original connection.

41. Translating Bridges • Translating bridges connect two LANs that use different data link protocols. • Performs the same functions as a transparent bridge. • Instead of forwarding the data to the other network, the bridge must provide translation. • Frame must be converted to a different format and run at a different speed. • Bridge provides buffer and negotiate the frame size and speed.

42. Router • A router is a device that chooses the best possible path for data frame transmission. • Uses software control to prevent traffic congestion. • Operates at the network layer of OSI model. • Routers must be able t communicate using the same protocols at both data link and network layers. • Multi-protocol routers provide address translation for networks with different operating systems.

43. Router • Routers examine frames that are specifically address to them. • It looks at the logical address (assigned by network administrator). • Frames not addressed to the router are ignored. • Routers can split packets into fragments. • Routers use flow control to prevent congestion. • Routers can monitor bandwidth of a path for problems.

44. Routing • Types of routing and routers • Dynamic • Changes are made dynamically to the routing table. • Static • Uses a a predetermined routing table constructed by network personnel.

45. Storage routers • Storage routers are used in Storage Area Networks (SAN). • Enables users to connect switched storage environments on a standard data network. • Used to build a separate network infrastructure for a SAN.

46. Brouter • A Brouter is a hybrid device that performs bridging and routing functions. • Examines frame and checks the destination address • If a frame is going to a LAN using a different protocol, the frame is bridged. • Brouters are generally slower than bridges and routers

47. Gateways • A Gateway uses software to connect networks with different architectures by performing protocol conversion. • Most complex device that will connect networks. • Operates at all seven layers of OSI model. • Can provide terminal emulation for workstations wanting to emulate dumb terminals. • Also provides for file-sharing and peer-to-peer communications between LAN and host. • Provide error detection and monitor traffic flow.

48. Hubs • Hubs physically connect cables. • A hub is usually the center or central node of a star topology. • Sometimes referred to as concentrators.

49. Modular Hubs • Modular hubs use a high-speed bus to link the various modules in the unit. • Capable of providing single or multiprotocol links (i.e. Ethernet, token-ring, FDDI, etc, can be mixed). • Multiple modular hubs can be linked via a bridge. • Provide flexibility when different backbone technologies have to converge.

50. Stackable hubs • Stackable hubs are generally single protocol devices. • Used to connect PCs of the same protocol. • Units can be cascaded together through Ethernet running over a twisted-pair drop cable. • Some shared bus scheme may be used to allow data to flow between stacked units.